var line = doc.getLine(pos.line);

      var leadLength = 0;

      var prefixChar = '';

      var whitespace = false;

      for (var i = pos.ch-1; i >=0; i--) {

        var ch = line[i];

        if (!whitespace && this._isIdentifierChar(ch)) {

          leadLength++;

          continue;

        }

        whitespace = /\s/.test(ch);

        if (!whitespace) {

          prefixChar = ch;

          break;

        }

      }

      var tailLength = 0;

      var suffixChar = '';

      whitespace = false;

      for (var i = pos.ch; i <line.length; i++) {

        var ch = line[i];

        if (!whitespace && this._isIdentifierChar(ch)) {

          tailLength++;

          continue;

        }

        whitespace = /\s/.test(ch);

        if (!whitespace) {

          suffixChar = ch;

          break;

        }

      }

      return {

        pos: pos,

        offset: offset,

        line: line,

        leadLength: leadLength,

        prefixChar: prefixChar,

        tailLength: tailLength,

        suffixChar: suffixChar

      };

    }

    /** More specifially, number or identifier (numbers, letters, underscore and dollar). */

    private _isIdentifierChar(ch: string): boolean {

      if (ch.toLowerCase()!==ch.toUpperCase())

        return true;

      else if (ch==='_' || ch==='$')

        return true;

      else if (ch>='0' && ch<='9')

        return true;

      else

        return false;

    }

    private _initEditor() {

      var options = this._shared.options || CodeMirrorEditor.standardEditorConfiguration();

      this._shared.cm = new CodeMirror(

        (element) => this._shared.element = element,

        options);

    }

    private _initDoc() {

      // resolve options (allow override)

      var options = this._shared.options || CodeMirrorEditor.standardEditorConfiguration();

      this._doc =

        options.mode ? new CodeMirror.Doc('', options.mode) :

        new CodeMirror.Doc('');

      this._positionOnOpen = true;

      // invoke overridable handleLoad()